Process for separating solid particles from suspension



' lower pressure.

NILS PEDEBSEN, OF BORREQAARD VIA. SARPSBORG, NORWAY.

, PROCESS FOR SEPARA'IING SOLID PARTICLES FROM SUSPENSION.

No Drawing.

To all whom it may concern:

Be it known that I, NILs PEDERSEN, a subject of the Kin of Norway, of Borregaard via Sarpsborg, orway, have invented certain new and useful Improvements in Processes for Separating Solid Particles from Suspensions; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

It is well known to separate solid substances from a suspension by means of air bubbles introduced or created in a liquid.

In the usual processes for such separation, for instance the known ore flotation process, the air bubbles are produced either by bein introduced below the surface of the liqui by means of an ejector or the like, or by being beaten into the liquid in a mixer at atmospheric pressure andliberated at a The first named methods possess the disadvantage that it is difficult to obtain sufficiently fine air bubbles, and the last named method has the disadvantage that it is diflicult to obtain a sufficient .absorption of air into the liquid.

According to the present invention the liquid is caused to absorb air or other gas under pressure, but the liberation of the air or gas thus introduced in the liquid takes cordmg to any other process.

place at atmospheric pressure. In this manner it is possible by regulating the pressure during the absorption to determine exactly the quantity of air absorbed in the liquid, said quantity being mainly dependent upon the pressure during the process of absorption.

The air bubbles and the distribution of the same obtained in this manner are infifiner than the bubbles obtained ac- The liquid owing to the fine air bubbles ac uires a milky color, and the fine air bubb es pronitely duced have proved to have a great aflinity' to the solid particles suspended in the liquid. For carrying out the process a mixer of i any known construction may be used provided the same is adapted to be put under pressure. From the mixer the l1qu1d 1s conducted to a separating vessel 1n wh1ch the Specification of Letters Patent.

Application filed September 8, 1918. Serial No. 252,485.

'he'ring bubbles, but also by the risin Patented May 3, 1921.

air bubblesare liberated and carry the susended solid particles with them-to the S111? ace.

My invention is particularly applicable to the separatlon of the fiber from the waste liquor of pulp factories. The high pressure an or other gas, for example, waste gases from the pulp manufacture, is forced by ets 1nto a body of liquid containing the fiber in a closed chamber capable of sustaining the pressure.

The liquor is preferably continuously supplied to and discharged from the chamber during the introduction of the gas or air. It appears that the compressed air or gas displaces some of the liquid absorbed by the fibers and at the same time is absorbed by the liquid in and surrounding the fibers, so that when the liquid and fibers are suddenl relieved from pressure the as bubbles will surround each fiber along its entire length and rapidly lift it to the surface. These bubbles adhering to the individual fibers will keep the fibers at the surface of the liquid for a considerable time before they coalesce, and break. The rise of the fibers through the liquid is not only assisted by their adbeneath them of a multitude of other bu bles not attached to the fibers.

The speed with which the fibers are caused to rise to the surface of the liquid, as well as the length of time the fibers remain at the surface depends entirely upon the pressure employed, and this I vary, according to circumstances and conditions of operating at the plant where the process is used.

As stated the method above described is particularly adapted for separating wood fibers suspended in the outlet water from various kinds of wood pulp plants, but the process may also be used in connection with the known methods for separation of ore.

I claim:

1. The process of separating fibers from waste liquors of paper mills, which comprises subjecting the liquor to stirring while under pressure and wh1le introducing a as under pressure and then dischargin the 11quid and permitting the liberation o the gas.

2. The process of separating fibers from waste liquors of paper mills, which comprises introducing air or gas under a presas my invention, I have signed my name in gurie exceeding atmospheric pressure into a presence of two subscribing witnesses.

o y of said liquorin a closed. chamber regulating the pressure during absorption NILS PEDERSEN' 5 and liberating the mixture at atmospheric "Witnesses:

pressure. C. FABRIoiUs HANSEN,

In testimony that I claim the foregoing C. NORMAN. 

